Looking Up column: Trio of planets herald the sunrise

Peter Becker More Content Now

Friday

Apr 10, 2020 at 10:08 AMApr 10, 2020 at 10:08 AM

Early risers (or really late get-to-bedders) have an astronomical treat awaiting them in the southeastern sky. Three planets, Mars, Saturn and Jupiter adorn the twilight glow, in that order from left to right.

This order assumes you are in the Northern Hemisphere. If you’re looking from say, Easter Island or Madagascar below the equator, the whole sky is flipped over from the perspective of those of us who are “Up Over” (opposite of Down Under).

Either way, a good time to look is about an hour before sunrise. That means around 5:30 a.m. daylight savings time.

Mars is the reddish one (magnitude 0.6). Saturn appears white and is nearly equal in brightness with Mars. Jupiter is quite bright, magnitude -2.2.

It is interesting to observe them night to night, and see how the planets shift in respect to each other and the stars.

A small telescope will show Mars as a tiny reddish disc; Saturn with its ring system and brightest moon, Titan, appearing as a dim star; and Jupiter as a squat disc, with dark bands and its four moons.

See the last quarter moon, to the lower right of Jupiter, on April 14, and watch the moon pass Saturn and Mars over the next two mornings.

The eclipticThe major planets, Mercury through Neptune, all follow roughly the same track across the sky, as they orbit the sun. The moon also keeps to the same track, as it goes around the Earth.

The planets deviate from the ecliptic in varying amounts, all within six degrees north or south of the centerline, which the sun appears to follow (as we on Earth go around it once a year).

If the orbits of the planets all exactly coincided, as they go there would be frequent eclipses (called “transits”), as a closer planet passes right in front of the other, as seen from our vantage point. That would be spectacular indeed, especially if two or more brighter planets converged. As it is, even a single pairing is exceedingly rare.

The last time was in 1818 when Venus transited the face of Jupiter. The next time is in 45 years, on Nov. 22, 2065, when Venus and Jupiter do it again. In 2067, Mercury passes in front of Neptune.

Jean Meeus wrote in Mathematical Astronomy Morsels (Willmann-Bell, 1997) that the eight planets only line up within one degree of each other (let alone actually overlap their discs) once every 13.4 trillion years. According to standard theory, by that time the Sun will be a red giant and engulf Mercury and Venus, while letting the other planets drift into radically different orbits long before such a lineup ever happens.

The moon’s orbit is inclined by 5 1/2 degrees from the ecliptic, so an eclipse only occurs when it is on or near it. Otherwise, we’d have a solar and a lunar eclipse every month, and it might not be quite as special when it happens!

The planets are all on nearly the same plane with the sun because there was no other flight that day heading that way. (Sorry.) They are all on roughly the same track because the planets all formed from the same flat, spinning disc of dust, back in the days of creation.

Meanwhile, don’t neglect Venus in the evening sky. Look due west for this gloriously bright planet, shining at magnitude -4.6.Keep looking up at the sky!

Peter Becker is managing editor at The News Eagle in Hawley, Pennsylvania. Notes are welcome at news@neagle.com. Please mention in what newspaper or website you read this column.